Dotmp kit formulations for radioisotopes

ABSTRACT

This invention relates to a Kit formulation to prepare a radioactive, bone-seeking, pharmaceutical drug that has high radiochemical purity (RCP) in a fast, facile and reproducible process. The Kit has at least two vials and a two-part buffer system with instructions on how to make the drug formulation in a radiopharmacy. The drug formulations of this invention can be conveniently and reproducibly prepared with better delivery of the drug to mammals, better radiochemical purity of the formulation for use in treating a mammal having bone pain, one or more calcific tumors or needing bone marrow suppression or bone marrow ablation.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under SBIR grant numberR44CA150601 awarded by NIH. The government has certain rights in theinvention.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to a Kit (defined below in the Glossary)formulation for bone-seeking radioactive metal-chelant compositionshaving DOTMP as the chelant that are suitable for administration to apatient or animal having bone pain, one or more calcific tumors, orneeding bone marrow suppression or bone marrow ablation.

Description of Related Art

Numerous pharmaceutical formulations for injection into a patient havebeen developed. Many formulations for injection into a mammal usebuffers for various purposes. For example, some cancer treatmentformulations for bone tumors containingN-3-bis(2-chloroethyl)-1,3,2-oxazaphosphinan-2-amide-2-oxide(ifosfamide, U.S. Pat. No. 6,906,047) use one buffer and noradioisotope.

U.S. Pat. No. 8,716,279 describes a formulation of benzodiazepinecompositions that are formulated for intranasal administration,comprising a binary solvent system comprising a first solvent in whichthe benzodiazepine is soluble, the first solvent capable of penetratingnasal mucosal tissue, and a second solvent in which the benzodiazepinein less soluble. Thus a two component system is used but no radioisotopeis present.

A radiopharmaceutical “kit” is a vial or vials containing necessarycomponents that are combined, following prescribed instructions, with aradioisotope to prepare a radiopharmaceutical. This preparation isgenerally performed at a radiopharmacy, which then transports the drugto a nearby clinical facility for administration. The advantages of suchsystems are that kits can have long shelf lives and can be storedon-site at a radiopharmacy. Medical radioisotopes generally have shorthalf-lives (e.g. Tc-99m is 6 hr and Y-90 is 64 hr) and once combinedinto a radiopharmaceutical can begin to radiolytically degrade the othercomponents of the drug.

Examples of kits used to prepare radiopharmaceuticals in this fashionare Cardiolite® (trademark of Lantheus Medical Imaging, Inc.) kit forthe preparation of technetium Tc99m sestamibi (NDC 11994-001), Ceretec™(trademark of GE Healthcare Limited) kit for the preparation oftechnetium Tc99m exametazime (NDC 17156-022) and Zevalin® (trademark ofRIT Oncology, LLC) kit for the preparation of yttrium Y-90 ibritumomabtiuxetan (NDC 68152-103).

Radiopharmaceuticals based on metal-chelant complexes have been used todiagnose and treat bone cancer. Another example is Quadramet® (trademarkof Lantheus Medical Imaging, Inc.), a commercially available chelateformed between Sm-153 and ethylenediaminetetramethylenephosphonic acid(EDTMP) that is currently indicated for the pain associated with bonemetastases (U.S. Pat. No. 4,898,724). Typical dosages are 1 mCi ofSm-153 per kg body weight of the patient. Thus for a 70 kg patient thedosage would be 70 mCi. Quadramet is produced at a central facility,dispensed and shipped frozen on dry ice in order to reduce radiolyticdegradation. This formulation is not a kit but rather the finalformulation ordered for a specific patent and shipped to theradiopharmacy to determine the dose for the patient.

U.S. Pat. No. 5,066,478 teaches a kit for the preparation of Sm-153EDTMP that was developed but was never commercialized. This kit was madeby lyophilizing EDTMP and an empirically determined excess of NaOH. Thelyophilized chelant was reconstituted with Sm-153 in 5 mL of 0.1 N HClor HNO₃, mixed well and the desired Sm-EDTMP complex was formed havingthe correct pH for injection. The ratio of EDTMP to Sm was about 300:1.However, a concern was the presence of excess chelant which can bind tocalcium ions and potentially stop the heart. Therefore a further kithaving 1 eq. of calcium was also made (EP Patent 462,787). Thelyophilized vial contained Ca-EDTMP and excess NaOH.

U.S. Pat. No. 5,059,412 teaches the use of Sm-153, Gd-159, Ho-166,Lu-177 and Yb-175 chelates with chelants derived from the1,4,7,10-tetraazacyclododecane moiety including1,4,7,10-tetraazacyclododecanetetramethylenephosphonic acid (DOTMP),while U.S. Pat. No. 5,064,633 teaches the above metals plus Y-90.Compositions of Sm, Gd, Ho, Lu and Y with DOTMP comprising predominatelynon-radioactive metal with the corresponding radioactive metal (e.g.Sm-152 with Sm-153 at μCi levels) were prepared and biodistribution datain rats was obtained. A kit formulation was made that had a first vialcontaining DOTMP and an empirically determined amount of NaOH which wasreconstituted with Ho-166 in 5.0 mL of 0.1 N HCl or HNO₃ to form aHo-DOTMP complex at pH 9-10. It is crucial that the pH not exceed 11 ormetal hydroxide will be formed. Likewise if the pH falls below 8, theDOTMP is protonated and the formation of the complex is impeded. Thevolume of acid added was critical to achieving this proper pH range soan automated syringe pump system was used to assure precise delivery ofthis volume. No buffers were used to achieve this pH range.

US Published Appln. 20020176818 teaches that Ho-166-DOTMP, a bone marrowsuppressing radionuclide composition, is formed by adding a Ho-166 salt,such as the chloride or nitrate in aqueous HCl (0.1-1N) or HNO₃, to asterile, evacuated vial containing at least 3 equivalents of DOTMP inaqueous base (KOH, NaOH and the like). Similar pH control issues arepresent as before in U.S. Pat. No. 5,059,412. After stirring at a pH of10.5, for 10 minutes, the pH is then adjusted to 7-8 by adding phosphatebuffer and a stabilizing agent such as ascorbic acid. Complexationof >99% is achieved.

A therapeutically effective biodistribution (fate of the activity afteradministration to a mammal) for a therapeutic bone agent includes highbone uptake, low soft tissue uptake, rapid clearance of the activity notassociated with bone, and high lesion-to-normal bone ratio. Compositionsthat do not have all of these characteristics are detrimental to thepatient. For example, high soft tissue uptake would result in thepatient receiving a high radiation dose to the liver, spleen or othersoft tissue leading to undesirable side effects.

One difficulty in many radionuclide complex formulations is obtaining ahigh radiochemical purity (RCP) of the complex, as well as maintainingthe RCP after it is made until it is injected. The radionuclide causesradiolytic degradation of the complex over time. Having a formulationthat has a high RCP for injection, while still being reliable andreproducible to make, has proven difficult.

Clearly, there is a need for a product with a high RCP while controllingthe process to prepare it.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a non-radioactive Kit formulation that isused to prepare a radioactive drug, which drug is used for the treatmentof a mammal comprising administration to the mammal having bone pain,one or more calcific tumors, or in need of a bone marrow suppressing orablation procedure. The invention provides a pharmaceutically-acceptableformulation of a Radioisotope chelate composition made from the Kit,said drug comprising a therapeutically effective amount of the complex.The Kit possesses a two-part buffer system, namely, Carbonate followedby Phosphate. The chelate is prepared from a Radioisotope selected froma group consisting of Sm-153, Gd-159, Ho-166, Lu-177 and Y-90 and DOTMPor a physiologically-acceptable salt thereof, which is part of one ofthe components of the Kit. The drug is prepared from the components ofthe Kit. The process to prepare the drug from this Kit is provided asinstructions with the Kit, as a package insert, or available on-linewith the purchase of the Kit.

The present invention provides a pharmaceutically-acceptable Kitformulation for the preparation of a radioactive bone-seeking drugcomprising at least two components, having a two-part buffering system,including instructions for its use, for preparing apharmaceutically-acceptable drug formulation of a Radioisotope-DOTMPchelate, wherein the Kit components are:

Vial 1: lyophilized DOTMP, Carbonate and NaOH or KOH;

Vial 2: optionally a Calcium solution in a pharmaceutically-acceptableaqueous solvent; and

Vial 3: a Phosphate buffer in a pharmaceutically-acceptable aqueoussolvent at a pH of about 7, optionally with pharmaceutically-acceptablepreservatives, diluents, and excipient;

provided that when then Kit is constituted to form the drug at the timeof use,

a Radioisotope selected from the group consisting of Sm-153, Gd-159,Ho-166, Lu-177, and Y-90 in HCl or HNO₃ is added to Vial 1 to achieve apH of 9-10 and then adding Vial 2 and Vial 3 to form the drug.

The formulation of this invention comprises a chelant composition as aKit having at least two separate components that form the Kit, whichincludes a two-part buffer system, which components are mixed in aprescribed manner with a Radioisotope to form the chelate composition atthe appropriate time prior to its use as a drug.

The present invention provides a process for the preparation of apharmaceutically-acceptable drug formulation using the Kit describedabove, which comprises the steps of:

a) reconstituting the lyophilized Vial 1 having Carbonate, DOTMP andNaOH or KOH, with a Radioisotope in HCl or HNO₃; and

wherein the Carbonate buffers at pH to about 9-10 so that theRadioisotope-DOTMP complex forms readily with an initial RCP of at least97%;

b) optionally adding to Vial 1, Vial 2, a Calcium solution, to theRadioisotope-DOTMP of step a); and

c) adding Vial 3, Phosphate buffer, to the prior formed solution of stepa) or b) to bring the pH to about 7-8 suitable for injection into amammal

The two-part buffer system provides critical pH control during twoseparate steps in the preparation process of the drug. Specifically, thesolution from which the lyophilized component 1 is prepared has a largeexcess of NaOH or KOH over the Carbonate present thereby having a veryhigh pH but no buffering capacity. The large excess of NaOH or KOH ispresent to neutralize the future addition of Radioisotope solution inHCl or HNO₃ when the Kit is used to prepare the drug. Once the acid isneutralized, the small amount of

Carbonate now provides buffering of the solution at pH of 9-10. This pHof 9-10 is the optimal range for chelate formation. When the prescribedvolume of acid is added to component 1 no further pH adjustment isrequired. Thus this first step of the Kit process is fast and facile.When component 3 (Phosphate) is added, the amount of Phosphate presentis designed to overwhelm the amount of Carbonate present therebybuffering the final drug solution at pH 7-8 and providing optimalosmolality suitable for injection. Therefore, the Kit provides for thepreparation of the drug in a fast and facile manner without further pHadjustments or other manipulations while still providing RCP of at least97% in a consistent and reproducible manner by the radiopharmacy.Radiolytic degradation of the drug is minimized after its preparation bythe radiopharmacy as the drug may be injected a short time thereafter toa mammal. No stabilizing agent (e.g. ascorbic acid) is required but mayoptionally be used.

The drug made from the above Kit is used in a method of treating amammal having disease causing bone pain, one or more calcific tumors orneeding bone marrow suppression or bone marrow ablation byadministration to said mammal this drug formulation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically shows the data for NaOH and DOTMP titrated with 0.1 NHCl. The steep titration curve illustrates the very narrow volume rangeof acid required to achieve the desired pH range of 9-10 for optimalchelation.

FIG. 2 graphically shows the data for Carbonate, NaOH and DOTMP titratedwith 0.1 N HCl. The desired pH range of 9-10 can be achieved using arelatively wide variation in acid volume thereby making radiopharmacypreparation of the drug reliably reproducible.

DETAILED DESCRIPTION OF THE INVENTION

It is understood that the terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting. As used in this specification, the singular forms “a”, “an”,and “the” include plural referents unless the content clearly indicatesotherwise. The following terms in the Glossary as used in thisapplication are to be defined as stated below and for these terms, thesingular includes the plural.

Various headings are present to aid the reader, but are not theexclusive location of all aspects of that referenced subject matter andare not to be construed as limiting the location of such discussion.

Also, certain US patents and PCT published applications have beenincorporated by reference. However, the text of such patents is onlyincorporated by reference to the extent that no conflict exists betweensuch text and other statements set forth herein. In the event of suchconflict, then any such conflicting text in such incorporated byreference US patent or PCT application is specifically not soincorporated in this patent.

Glossary

Calcium solution means an aqueous solution of calcium such as can beprepared from calcium chloride or calcium nitrate

Carbonate means pharmaceutically-acceptable NaHCO₃, Na₂CO₃, KHCO₃ orKCO₃ and mixtures thereof which, under appropriate conditions, have theability to buffer at pH 9-10

Ci means curies

Chelate and Complex are used interchangeably and mean a metal bound to achelant (noun) or the act of forming this bound combination (verb)

μCi means microcuries

mCi means millicuries

DOTMP means1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylenephosphonic acid

EDTMP means ethylenediaminetetramethylenephosphonic acid

eq. means equivalent

hr means hour(s)

Kit means a vial or vials containing necessary components that arecombined, following prescribed instructions, with a radioisotope toprepare a radiopharmaceutical

FDA means US Food and Drug Administration including its regulationsMammal means warm-blooded animals including humans min. means minutes

Phosphate buffer means pharmaceutically-acceptable mono-, di- ortri-phosphate buffer or mixtures thereof

QC means quality control

Radioisotopes means Sm-153, Gd-159, Ho-166, Lu-177 and Y-90 and includestheir cold isotopes, a subset of radionuclides

RCP means radiochemical purity, the proportion (expressed as percent) ofthe total activity of a specific radionuclide in a specific chemical orbiologic form

Discussion

As Radioisotope-DOTMP chelates are more thermodynamically stable thanare Radioisotope-EDTMP chelates; the ratio of DOTMP to Radioisotope canbe as low as about 1:1 (as a safeguard 3:1 as a minimum), rather than aminimum of about 300:1 as is required for EDTMP to Radioisotope. Thispresent formulation is used to treat a mammal having bone pain, one ormore calcific tumors, or needing bone marrow suppression or bone marrowablation.

The kit of the present invention can be used for the convenient andreliable radiopharmacy preparation of a bone-seeking radioactivelanthanide (e.g. Sm-153, Gd-159, Ho-166, Lu-177 or Y-90) chelates ofDOTMP. Radiopharmacy preparation offers a crucial advantage over centralmanufacturing because radiolytic degradation of the formulated drug isminimized

Three indications for the resulting present bone-seekingradiopharmaceutical formulations are envisioned. A low-dose formulation(0.5-1.0 mCi/kg) can be used to treat metastatic bone cancer arisingfrom another primary site (e.g. prostate, breast, lung). A repeateddosing regimen has shown efficacy in treating metastatic bone cancer andthe kit method can make this much more convenient.

A high-dose bone-seeking radiopharmaceutical formulation (5-30 mCi/kg)can be used to treat primary bone cancers such as osteosarcoma. Theseformulations may optionally be used as companion treatment to externalbeam radiotherapy.

A high-dose formulation (20-40 mCi/kg) can also be used to ablate bonemarrow as a pretreatment for bone marrow transplant. Many diseases (e.g.myelodysplastic syndrome, leukemia, multiple myeloma, sickle cellanemia) can be treated by a successful bone marrow transplant and highdose radiopharmaceutical ablation offers a potentially safer method(compared to high dose chemotherapy and/or total body radiation).

Two different kit formulations are envisioned. A low-dose kit for thepreparation of bone-seeking radiopharmaceuticals for the treatment ofmetastatic bone cancer and a high-dose kit for the preparation ofbone-seeking radiopharmaceuticals for the treatment of osteosarcoma andfor bone marrow ablation.

Low-dose kits will support the production of up to 300 mCi per vial andhigh-dose kits can be used to prepare up to 3 Ci per vial. Both kitsreliably provide for an initial pH range of about 9-10, which is optimalfor the formation of lanthanide metal DOTMP chelates, and a final pHrange of about 6.5-7.5 and osmolality between 300 and 400, which makethe drug suitable for injection into a patient.

When the desired Radioisotope-DOTMP complex for the present formulationis prepared, various issues arise when compared to making the Sm-EDTMPcomplex. After much testing it became apparent that the steps of how itis made are important to control these issues. It is difficult tomanually deliver a precise volume of Radioisotope in acid solution tothe Kit at the radiopharmacy where the syringe is in a shield, operatedbehind another shield and in a laminar flow hood. This makes itdifficult to manipulate the syringe; thus making it problematic toreliably achieve the desired narrow pH range. Because of the steeptitration curve in the desired pH range to form these complexes (FIG.1), the volume of acid added must be precisely controlled. The pH alsodepends on the amount of metal dissolved in the HCl or HNO₃ and theresulting ratio of the HCl or HNO₃ to the NaOH or KOH. Thus as theamount of metal varies (e.g. using different activities of Radioisotopeto prepare different prescribed dosages for different patients), it inturn affects both the concentration of acid (e.g. HCl or HNO₃) and thevolume of acid required to achieve the desired pH range. This presentKit makes the reconstitution easier for a radiopharmacy to quickly,consistently and reliably obtain the desired pH. A pH range of 9-10 isrequired to optimally form the Radioisotope-DOTMP complex. If the pH isoutside this range, then the desired complex does not form as well orcan require extended manipulation such as pH adjustment or heating thatresults in additional time required. This can result in a low RCP and afailed QC test. If injected into a mammal, a drug with low RCP canresult in a poor biodistribution of the drug in the mammal. This resultcan be costly or impossible to correct. The present Kit is reliable toobtain the desired pH for anywhere from trace amounts of metal up toone-third molar equivalent based on DOTMP (e.g., for 10 mg of DOTMP (18micromoles) 6 micromoles of metal can be used) and with much largervariations in the volume of acidic Radioisotope solution added. Withoutthe Carbonate buffer present it is very difficult to obtain the targetpH range consistently.

Another issue is when calcium is added, if desired, for the reasons asnoted above. In an attempt to further streamline the drug preparation, a2 vial Kit was prepared where vial 1 had lyophilized Ca-DOTMP withexcess NaOH and vial 2 had Phosphate buffer. This worked well when onlytrace amounts of Radioisotope were used, but the complexation did notwork well when the ratio of DOTMP to metal, e.g. Sm, was about 3:1. Thusthe presence of calcium created problems with forming theRadioisotope-DOTMP complex and adversely affected the RCP of the desiredcomplex. This problem was unexpected because, as noted above, thisstrategy worked with Ca-EDTMP. Additionally since Sm-DOTMP isthermodynamically more stable than Ca-DOTMP it was expected that Smwould readily displace Ca in the complex as it does in the case ofCa-EDTMP.

How to overcome these issues and have a reproducible formulation fordose to a patient or mammal is one purpose of this invention. What hasbeen found is that in contrast to the past Kits for similar drugs, forthis invention it is necessary to have a Kit containing 2 to 3 vialsfrom which the formulation is prepared. A two-part buffer system isneeded to accurately control the pH during two steps of the process,first at 9-10 for optimal formation of the complex then at 7-8 foradministration to a patient. Thus the Kit consists of the following:vial 1 has lyophilized Carbonate, DOTMP and NaOH or KOH. This vial isreconstituted with Radioisotope in HCl or HNO₃ as supplied by themanufacturer of the Radioisotope. This Radioisotope solution in aqueousHCl or HNO₃ is added to vial 1 where the NaOH or KOH neutralizes the HClor HNO₃ and the Carbonate becomes a buffer and maintains the solution atpH 9-10 so that the complex of Radioisotope-DOTMP forms immediately witha high RCP (at least 97%). No calcium is present in the solution at thispoint to interfere with the kinetics of complex formation. Optional vial2 contains Calcium solution and can be added next. Vial 3 has Phosphatebuffer at about pH 7 that is added to the prior formed solution to bringthe pH down to 7-8 for injection into a mammal.

The following scheme using Sm-153 is provided to assist in understandingthis process. Preferably all of the process is done according to FDArequirements for a drug manufacturing process and sterile conditionsusing appropriate safety equipment for radioisotopes.

Vial 1 is a lyophilized mixture prepared from DOTMP (10 mg, 18.2micromoles), and an empirically determined amount of NaOH (21.9 mg), andNaHCO₃ (10.7 mg) (which becomes a Carbonate buffer after the addition ofacid);

Vial 1 is reconstituted with about 4.0 mL of Sm-153 (as SmCl₃ solutionpresent with other Sm isotopes such as Sm-152) in 0.1 N HCl; total Smmass per 10 mg of DOTMP must not exceed 1.38 mg (6 micromoles); the vialis then inverted or gently shaken to agitate the solution to have allsolids dissolve;

A minimal QC sample (about 1-10 microliters) is removed for testing pH(expected to be 9-10) and RCP (expected to be ≥97%). Both of thesevalues must be met to proceed. The pH is checked with pH strips and theRCP is determined using one of a number of known methods which could beused; in this present application RCP was determined using a SPSephadex® column eluted with saline; Sm-153 activity is measured tocalculate RCP by the formula:

${{{RCP}\left( {\% \mspace{14mu} {Complex}} \right)} = {\left\lbrack \frac{\mu \; {Ci}_{eluate}}{{\mu \; {Ci}_{eluate}} + {\mu \; {Ci}_{column}}} \right\rbrack \times 100}};$

Vial 2 has a solution of 36.5 mM CaCl₂ where 0.5 mL of this Vial 2solution (18.2 micromole) is added to the solution of Vial 1 andinverted or gently agitated to mix the contents; although this vial isoften desired, it is optional; this addition must be done prior toadding the second buffer;

Vial 3 contains 0.5 M Phosphate buffer (pH 7) as a second buffer where0.5 mL of the solution from this Vial 3 is added to Vial 1 and invertedor gently agitated to mix the contents;

A minimal QC sample is removed for testing pH (expected to be 7-8) andRCP (expected to be ≥97%). To be suitable for use, both values must bemet. The pH is checked with pH strips and the RCP is determined asbefore; and

The activity of Sm-153-DOTMP solution is measured using a dosecalibrator.

This provides the drug formulation used for injection to a mammal.

It has been found that each of these steps must be done in the orderspecified or undesired results occur. For example, if the Phosphatebuffer is added before the Calcium solution, a precipitate of calciumphosphate will be formed even though the DOTMP chelant is present.Therefore if Calcium solution is used, it must be present in theformulated solution prior to the addition of the second buffer. If theCalcium solution in vial 2 is added to the DOTMP in vial 1 before the Smor other Radioisotope solution is added, the calcium will interfere withthe complexation. A pH of pH 9-10 is required to optimally complex theSm with DOTMP which is not easily achieved without the Carbonate buffer.This pH is the range where the complex forms with best RCP and in thequickest time, but no other competing ions, such as calcium, should bepresent to interfere with the desired complex formation. The Carbonatebuffer (e.g., sodium carbonate or other physiologically-acceptableCarbonate buffers or mixtures thereof) maintains this narrow pH range,buffering in the 9-10 region. Later a second buffer (sodium phosphate orother physiologically-acceptable Phosphate buffers or mixtures thereof)is used to bring the pH to 7-8 for injection of the formulated drug.Thus, to maintain pH control through this process, the Kit uses atwo-part buffer system.

In some instances it has been found that the calcium is not required inthe drug formulation at all. When used its main function is to preventthe DOTMP from complexing serum calcium in the body and causing ashortage of calcium that can potentially stop the heart. However, unlikeprior radionuclide complex drugs, there is not the excessive amount ofchelant present to be freely available to complex calcium in the body asthe chelant is present in a much lower amount. Thus this concern isminimized with this DOTMP chelant.

When the drug formulation is done in this manner, there is reliablyobtained a high RCP (at least 97%) and the pH and osmolarity aresuitable for injection. Additionally, formulation of the drug is a rapidprocess to minimize radiolytic degradation.

While not wishing to be bound by theory, it is believed that thekinetics of the complex formation, the thermodynamic stability of thecomplex, and the lack of competing metals are critical to achieve thehigh RCP when the desired metals are used in the narrow pH range.Suitable metals are Sm-153, Gd-159, Ho-166, Lu-177 and Y-90, with Sm-153or Lu-177 preferred, and Sm-153 especially preferred. It is understoodthat other isotopes of each metal are present with the radioactiveisotope. The chelant is DOTMP.

The formulation of the present invention is in a Kit form for aradiopharmacy to use to prepare the drug according to instructionsprovided either with the Kit component vials or separately such asavailable on-line with the Kit wherein the Kit comprises: DOTMP, firstbuffer Carbonate and acid-neutralizing NaOH or KOH (vial 1); the Calciumsolution (vial 2, optional); and the second buffer Phosphate (vial 3).The Radioisotope in HCl or HNO₃ would be delivered separately and thenthis process followed to make the drug. The components are mixed in thecorrect order at the appropriate time prior to use (at the hospitalpharmacy or radiopharmacy). The dose may be supplied as a unit dose in asyringe for a mammal. The formulation provides apharmaceutically-acceptable aqueous carrier for injection. The finaldrug may be a pharmaceutically-acceptable salt of the drug, such assodium salt, so long as the final osmolarity is from 154 to 600,preferably 300-400 mOsm/L for injection. The drug formulation isadministered to the mammal by injection intravenously.

The Components of Low-Dose and High-Dose Kits with Ranges:Low-Dose kits:

Vial 1 is a lyophilized mixture prepared from DOTMP (9-11 mg, preferably10 mg), and an empirically determined amount of NaOH (19.7-24.1 mg,preferably 21.9 mg), and NaHCO₃ (9.7-11.8 mg, preferably 10.7 mg) (whichbecomes a Carbonate buffer after the addition of acid solution);

Vial 1 is reconstituted with about 3.6-4.4 mL, preferably 4.0 mL of upto 300 mCi of Sm-153 (as SmCl₃ solution present with other Sm isotopessuch as Sm-152) in 0.1 N HCl;

Vial 2 contains a solution of 32.8-40.1 mM, preferably 36.5 mM, of CaCl₂where 0.45-0.55 mL, preferably 0.5 mL, of this Vial 2 solution is addedto the solution of Vial 1; although this vial is often desired, it isoptional; this addition must be done prior to adding the second buffer;

Vial 3 contains 0.45-0.55 M, preferably 0.5 M, of Phosphate buffer (pH7) as a second buffer where 0.45-0.55 mL, preferably 0.5 mL, of thesolution from this Vial 3 is added to Vial 1.

High-Dose kits:

Vial 1 is a lyophilized mixture prepared from DOTMP (90-110 mg,preferably 100 mg), and an empirically determined amount of NaOH(197-241 mg, preferably 219 mg), and NaHCO₃ (97-118 mg, preferably 107mg) (which becomes a Carbonate buffer after the addition of acidsolution);

Vial 1 is reconstituted with about 36-44 mL, preferably 40 mL, of up to3000 mCi of Sm-153 (as SmCl₃ solution present with other Sm isotopessuch as Sm-152) in 0.1 N HCl;

Vial 2 contains a solution of 328-401 mM, preferably 365 mM, of CaCl₂where 4.5-5.5 mL, preferably 5 mL of this Vial 2 solution is added tothe solution of Vial 1; although this vial is often desired, it isoptional; this addition must be done prior to adding the second buffer;

Vial 3 contains 4.5-5.5 M, preferably 5 M, of Phosphate buffer (pH 7) asa second buffer where 4.5-5.5 mL, preferably 5 mL of the solution fromthis Vial 3 is added to Vial 1.

In the following examples it can be noted that staying within thedesired pH range of 9 to 10 is optimal for chelation. When the pH fallsto 8 or rises to 11, the RCP of the Sm-DOTMP complex is adverselyaffected. In the absence of the Carbonate buffer, pH can also vary evenwhen a consistent volume of acid is added.

The invention will be further clarified by a consideration of thefollowing examples, which are intended to be purely exemplary of theinvention.

Materials and Equipment:

The radioactive isotopes were purchased from The University of MissouriResearch Reactor as solutions in 0.1N HCl.

Chelants were purchased from commercial sources or were prepared asdescribed in U.S. Pat. No. 5,059,412.

OLINDA/EXM software for internal dose assessment was acquired from theauthors (Stabin M G, Sparks R B, Crowe E. (J Nucl Med. 2005 Jun;46(6):1023-7).

The pH measurements were made using either an Oaktron pH700 pH meterwith Mettler Toledo InLab Micro probe or with Merck MColorpHast™pH-indicating strips (0-14).

Radioactivity was measured using a Capintec CRC-55t dose calibrator ionchamber/NaI well scintillation detector.

RCP was determined as discussed above.

General Procedure

In the following examples, the lettered examples are comparativeexamples or procedures, and the numbered examples are this presentinvention.

Example A: Preparation of lyophilized vials of Ca-DOTMP

Into 10 mL vials was dispensed 2.5 mL of the following solution: 1.00 gof DOTMP, 0.135 g of Ca(OH)₂, and 7.959 g of 10 N NaOH in 0.25 L ofdeionized water.

The vials were placed in a lyophilizer and freeze-dried. The amount ofNaOH in these vials was empirically determined using titrationexperiments. It was designed to neutralize a volume of 5.0 mL ofRadioisotope solution in 0.1N HCl and result in a pH of 9-10. Theselyophilized vials were then used in the following examples as indicated.

Example B: Preparation of Sm-153-DOTMP from lyophilized Ca-DOTMP, pH 11

Sm in HCl was prepared by adding 1.9 mg of non-radioactive Sm(NO₃)₃·6H₂O along with a trace amount of Sm-153 to 6 mL of 0.1 N HCl. This wasdone in order to use trace amounts of activity but mimic the amount ofSm metal that would be contained in much higher clinically relevantdoses. To a lyophilized Ca-DOTMP vial (prepared as in Example A) wasadded 4 mL (rather the 5 mL) of this Sm solution. This was done toevaluate the effect of high pH in combination with Ca on the complexformation. The resulting pH was 11 and the desired Sm-DOTMP complex wasonly partially formed as indicated by its RCP of 72%.

RCP was measured by adding a small drop of the sample to a 1-mL SephadexSP® column. Complexed samarium was eluted in two 1-2 mL fractions, whilefree (uncomplexed) Sm was retained on the column. Radioactivity wasmeasured in a dose calibrator, and RCP is represented as a simple ratioof activity in the combined elutions to the total activity in elutionsand the column.

Example C: Preparation of Sm-153-DOTMP from lyophilized Ca-DOTMP, pH 8

Sm in HCl was prepared by adding 1.4 mg of Sm(NO3)3.6 H₂O along with atrace amount of Sm-153 to 5.5 mL of 0.1 N HCl. To the lyophilized DOTMPvials (prepared as in Example A) was added 5.0 mL of this Sm solution.The pH of this Sm-DOTMP solution was 8, and RCP was 87%. This shows thatthe combination of Ca and pH 8 impedes complex formation. This alsodemonstrates that pH control by delivery of a precise volume of acid isdifficult as this formulation was designed to be in the pH range 9-10.

Example D: Preparation of Ca-DOTMP solution

A Ca-DOTMP solution was prepared from 40.4 mg of DOTMP, 5.2 mg ofCa(OH)₂, and 318.6 mg of 10 N NaOH, which volume was brought to a totalvolume of 10 mL with deionized water. The amount of NaOH in 2.5 mL ofthis solution was calculated based on prior titration experiments, toneutralize 5.0 mL of Radioisotope solution in 0.1N HCl and result in apH of 9-10.

Example E: Preparation of DOTMP solution

A DOTMP solution was prepared without calcium using 40.2 mg of DOTMP and202.0 mg of 50% NaOH in 10 mL of deionized water. The amount of NaOH in2.5 mL of this solution was calculated based on prior titrationexperiments, to neutralize 5.0 mL of Radioisotope solution in 0.1N HCland result in a pH of 9-10.

Example F: Preparation of Sm-153-DOTMP from Ca-DOTMP solution

The Ca-DOTMP solution (prepared as in Example D) was tested by adding Smsolution to 2.5 mL of that solution. The Sm solution was prepared from2.6 mg of Sm(NO₃)₃·6 H₂O, along with a trace amount of Sm-153 in 4 mL of0.1 N HCl. All 4 mL was then added to the 2.5 mL of the DOTMP solution.Its pH was 11, so additional 0.1 N HCl was slowly added until the pHreached 9. About 0.2 mL was required to adjust the pH.

Despite adjusting to the desired pH, RCP was only 88%. This shows that,even in the desired pH range, the presence of Ca interferes with thecomplex formation. This also again demonstrates that achieving thistarget pH range can be difficult as the total volume of acid added, 4.2mL, is less that the anticipated 5.0 mL.

Example G: Titration of DOTMP

DOTMP (10 mg) was dissolved in 10 N NaOH (72.6 mg) and deionized water(1 mL) in a 20 mL vial. This solution was titrated with 0.1N HCl. Theseresults are shown in Table 1 and in FIG. 1. These results demonstratethe difficulty of achieving the desired pH range upon reconstitution inthe absence of Carbonate buffer.

TABLE 1 Titration of DOTMP containing NaOH 0.1N HCl (mL) pH 2.0 13.392.2 13.32 2.4 13.24 2.6 13.15 2.8 13.04 3.0 12.94 3.2 12.80 3.4 12.643.6 12.41 3.8 12.05 4.0 10.87 4.1 10.40

4.3 8.53 4.4 7.78 4.5 6.93 4.6 6.31 4.7 5.82 4.8 5.15

The results show that there is no buffering in this formulation withinthe range of pH 9-10, which is optimal for Sm-DOTMP complex formation.The bold italicized box indicates the preferred pH range. Very precisemeasurement of acid is required to achieve this pH. This is difficult inthe case of radioactive compounds as they must be handled in a shieldedsystem that makes such precise measurements challenging.

EXAMPLE 1 Preparation of Lyophilized DOTMP Containing Carbonate

Into 10 mL vials was dispensed 2.5 mL of a solution prepared bycombining 99.9 mg of DOTMP, 726.5 mg of 10 N NaOH, and 107.3 mg ofNaHCO₃ in 25 mL of deionized water. The vials were placed in alyophilizer and freeze-dried. The amount of NaOH in these vials wasempirically determined using titration experiments. It was designed toneutralize a volume of 4.0 mL of Radioisotope solution in 0.1N HCl andbuffer in the pH range of 9-10.

EXAMPLE 2 Titration of Lyophilized DOTMP Containing Carbonate

A lyophilized vial of DOTMP containing Carbonate (prepared as inExample 1) was titrated with 0.1 N HCl. The Carbonate was shown to havebuffering capability in the region of interest, pH 9-10 (see Table 2 andFIG. 2). FIG. 2 shows this titration curve highlighting in grey thedesired pH range for the optimal formation of the complex. Contrast thiswith the titration curve of DOTMP without Carbonate buffer in FIG. 1(from Example G). The slope of the curve in FIG. 1 makes it difficult toalways achieve the desired pH without very precise delivery of acid;whereas the shallow slope in FIG. 2 enables the desired pH range to bemore readily obtained.

TABLE 2 Titration of lyophilized DOTMP containing Carbonate and NaOH0.1N HCl (mL) pH 1 13.05 2 12.52 2.5 12.12 2.7 11.83 2.9 11.37 3.1 10.823.2 10.59 3.3 10.44 3.4 10.28 3.5 10.15 3.6 10.04

4.4 8.8 4.6 8.07 4.8 7.33 5 6.89

The results show that the Carbonate present in the formulation ofExample 1 buffers within the range of pH 9-10, which is optimal forSm-DOTMP complex formation. The bold italicized boxes indicate thepreferred pH range.

EXAMPLE 3 Preparation of Sm-153 DOTMP with added Ca

A vial prepared as in Example 1 was reconstituted by adding 4.0 mL of atrace Sm-153 solution in 0.1N HCl prepared as in Example B. The pH was10 and the RCP was 99.7%. To this vial was added 0.5 mL 36.5 mM CaCl₂.To the resulting solution in this vial was next added 0.5 mL 0.5 MPhosphate. The pH was 7 and the RCP was 99.8%.

EXAMPLE 4 Preparation of Sm-153-DOTMP without added Ca

A vial prepared as in Example 1 was reconstituted by adding 4.0 mL of atrace Sm-153 solution in 0.1N HCl prepared as in Example B. The pH was10 and the RCP was 99.9%. To this vial was added 0.5 mL 0.5 M Phosphate.The pH was 7 and the RCP was 99.9%.

EXAMPLE 5 Rat Biodistribution

The formulations prepared in Example 3 (w/Ca) and Example 4 (w/out Ca)were each injected into the tail veins of three male Sprague-Dawleyrats. The rats weighed between 230 and 245 g each. After 2 hr, the ratswere sacrificed and the following organs and tissues were collected:blood, heart, lung, femur, muscle, liver, spleen, kidney, smallintestine, large intestine, stomach and brain. Also collected wereurine, feces, and the remainder of the body. The radioactivity in eachof these samples was measured and the percent injected dose (%ID) ineach was calculated. The results are shown in Table 3.

TABLE 3 Biodistribution of Sm-153-DOTMP both with and without added CaFormulation Formulation of Example 3 of Example 4 Blood 0.0% 0.1% Heart0.0% 0.0% Lung 0.0% 0.0% Bone 50.0% 51.6% Muscle 0.1% 0.1% Liver 0.1%0.1% Spleen 0.0% 0.0% Kidney 0.5% 0.6% Sm Int 0.7% 2.5% Lg. Int 0.6%0.1% Stomach 0.0% 0.6% Brain 0.0% 0.0% Bladder/Urine 46.2% 39.9%

These results demonstrate that the formulations of the present inventionboth with and without added Ca have a favorable biodistribution for atherapeutic bone agent (e.g., high bone uptake, low soft tissue uptake,and rapid clearance of the activity not associated with bone).

EXAMPLE 6 Process of Kit Formation

The following process scheme is provided to assist in understanding thesteps in this process. All of the process is done according to FDArequirements for a drug manufacturing process and using sterileconditions, and safety handling for radioactive drugs and isotopes.

Vial 1 contains a lyophilized mixture prepared from DOTMP (10 mg), NaOH(21.9 mg), and NaHCO₃ (10.7 mg, to form the Carbonate buffer);

Vial 1 is reconstituted with 4 mL of Sm-153 (as SmCl₃ solution) in 0.1 NHCl; total Sm mass per 10 mg of DOTMP must not exceed 1.38 mg;

Vial 1 is then inverted (or gently shaken) to agitate the solution andhave all solids dissolve;

A minimal QC sample (1-10 microliter) is removed for testing the pH(expected to be 9-10) and RCP (expected to be ≥97%). The pH is checkedwith a pH strip and the RCP is determined using a SP Sephadex® columneluted with saline; Sm-153 activity is measured to calculate RCP by theformula:

${{{RCP}\left( {\% \mspace{14mu} {Complex}} \right)} = {\left\lbrack \frac{\mu \; {Ci}_{eluate}}{{\mu \; {Ci}_{eluate}} + {\mu \; {Ci}_{column}}} \right\rbrack \times 100}};$

Vial 2 has a solution of 36.5 mM CaCl₂ where 0.5 mL of this Vial 2solution is added to the solution of Vial 1 and inverted to mix thecontents; although this vial is often desired, it is optional; thisaddition must be done prior to adding the second buffer;

Vial 3 contains 0.5 M sodium phosphate (pH 7) as a second buffer where0.5 mL of the solution from Vial 3 is added to Vial 1 and inverted tomix the contents;

A minimal QC sample is removed for testing the pH (expected to be 7-8)and RCP (expected to be ≥97%) as before; and

The activity of Sm-153-DOTMP complex solution is measured using a dosecalibrator.

EXAMPLE 7

A vial prepared as in Example 1 was reconstituted by adding 4.0 mL of asolution containing 307 mCi of Sm-153 in 0.1N HCl. The pH was between 9and 10 and the RCP was 98.6%. To this vial was added 0.5 mL 36.5 mM ofCaCl₂. To the resulting solution in this vial was next added 0.5 mL of0.5 M Phosphate. The solution was filtered through a 0.2 μm filter intoa sterile 10 mL vial. The final formulation contained 269.5 mCi, the pHwas 7 and the RCP was 98.0%.

EXAMPLE 8 Treatment of Osteosarcoma and Myelodysplastic Syndrome

A 25-year-old, 60 kg male patient presenting with both recurrentinoperable osteosarcoma and myelodysplastic syndrome was in need of abone marrow transplant. He was injected with a diagnostic dose, 1 mCi/kg(60 mCi) of the formulation of Example 7. The purpose of this diagnosticdose was to calculate the radiation dose to the marrow and other organsfor a proposed ablative dose prior to bone marrow transplantation.

A SPECT scan (Single Photon Emission Computed Tomography) at 1 hrrevealed that the Sm-153 was roughly evenly distributed between theskeletal system and the bladder and kidneys. No other soft tissue showedany activity. The kidneys and bladder were not visible in the 24-hr,48-hr and 7-day images. Long-term skeletal activity follows theradioactive half-life of Sm-153 (i.e., Sm-153-DOTMP remains bound tobone).

Using the skeletal uptake and clearance data, OLINDA 1.1 dosimetrysoftware was used to estimate that for a myeloablative dose of 30 mCi/kg(1800 mCi), the estimated radiation dose would be 38 Gy to red marrowand 8 Gy to kidneys. No other organs were expected to receive asignificant radiation dose. These estimates showed that the marrow couldbe safely ablated using the planed dose.

EXAMPLE 9 Preparation of High Dose Formulation from Kit

Nine vials prepared as in Example 1 were reconstituted by adding to each4.0 mL of a solution containing 237 mCi of Sm-153 in 0.1N HCl (totalactivity 2.1 Ci). The pH of each solution was between 9 and 10 and theRCP of each was between 98 and 100%. To each vial was added 0.5 mL of36.5 mM CaCl₂ followed by 0.5 mL of 0.5 M Phosphate. The solutions werefiltered through a 0.2 μm filter into a sterile 100 mL vial. The finalformulation contained 1,972 mCi, the pH was 7 and the RCP was 98.8%.

EXAMPLE 10 Treatment of the Patient with High Dose Kit

The patient of Example 8 was infused with 1.9 Ci of the formulation ofExample 9 in order to ablate the bone marrow to allow for subsequentbone marrow transplantation. The estimated radiation dose is 40 Gy tored marrow and 9 Gy to kidneys. The 48 hr image revealed no soft tissueactivity and only bone uptake was visible.

Bone marrow biopsy fourteen days post ablative dose revealed that bonemarrow had been successfully ablated. Stem cells from a matched donorwere administered. Clinical indicators such as white blood cell count,red blood cell count and platelet count indicated successful resolutionof myelodysplastic syndrome.

Although the invention has been described with reference to itspreferred embodiments, those of ordinary skill in the art may, uponreading and understanding this disclosure, appreciate changes andmodifications which may be made which do not depart from the scope andspirit of the invention as described above or claimed hereafter.Accordingly, this description is to be construed as illustrative onlyand is for the purpose of teaching those skilled in the art the generalmanner of carrying out the invention.

What is claimed is:
 1. A pharmaceutically-acceptable Kit formulation forthe preparation of a radioactive bone-seeking drug comprising at leasttwo components, having a two-part buffering system, includinginstructions for its use, for preparing a pharmaceutically-acceptabledrug formulation of a Radioisotope-DOTMP chelate, wherein the Kitcomponents are: Vial 1: lyophilized DOTMP, Carbonate and NaOH or KOH;Vial 2: optionally a Calcium solution in a pharmaceutically-acceptableaqueous solvent; and Vial 3: a Phosphate buffer in apharmaceutically-acceptable aqueous solvent at a pH of about 7,optionally with pharmaceutically-acceptable preservatives, diluents, andexcipient; provided that when then Kit is constituted to form the drugat the time of use, a Radioisotope selected from the group consisting ofSm-153, Gd-159, Ho-166, Lu-177, and Y-90 in HCl or HNO₃ is added to Vial1 to achieve a pH of 9-10 and then adding Vial 2 and Vial 3 to form thedrug.
 2. The Kit of claim 1, wherein the Radioisotope is Sm-153 orLu-177.
 3. The Kit of claim 1, wherein Vial 2 of Calcium is omitted. 4.The Kit of claim 1, wherein Vial 2 of Calcium is present.
 5. The Kit ofclaim 1 wherein the instructions for constitution of the drug areprovided as a part of the package insert with the Kit or are availableon-line with the Kit information.
 6. The Kit of claim 1 wherein the Kitis a low dose Kit having: Vial 1: about 9-11 mg of DOTMP; about19.7-24.1 mg of NaOH; about 9.7-11.8 mg of NaHCO3; reconstituted withabout 3.6-4.4 mL of up to 300 mCi of Radioisotope in 0.1 N HCl; Vial 2:about 32.8-40.1 mM of CaCl₂; and Vial 3: about 0.45-0.55 M of Phosphatebuffer (pH 7) as a second buffer.
 7. The Kit of claim 1 wherein the Kitis a high dose Kit having: Vial 1: about 90-110 mg of DOTMP; about197-241 mg of NaOH; about 97-118 mg of NaHCO₃; reconstituted with about36-44 mL of up to 3000 mCi of Radioisotope in 0.1 N HCl; Vial 2: about328-401 mM of CaCl₂; and Vial 3: about 4.5-5.5 M of Phosphate buffer (pH7) as a second buffer.
 8. A process for the preparation of apharmaceutically-acceptable drug formulation using the Kit of claim 1,which comprises the steps of: a) reconstituting the lyophilized Vial 1having Carbonate, DOTMP and NaOH or KOH, with a Radioisotope in HCl orHNO₃; and wherein the Carbonate buffers at pH to about 9-10 so that theRadioisotope-DOTMP complex forms readily with an initial RCP of at least97%; b) optionally adding to Vial 1, Vial 2, a Calcium solution, to theRadioisotope-DOTMP of step a); and c) adding Vial 3, Phosphate buffer,to the prior formed solution of step a) or b) to bring the pH to about7-8 suitable for injection into a mammal.
 9. The process of claim 8,wherein the drug formulation is a low dose formulation: Vial 1 is alyophilized mixture prepared from DOTMP (9-11 mg, preferably 10 mg), andan empirically determined amount of NaOH (19.7-24.1 mg, preferably 21.9mg), and NaHCO₃ (9.7-11.8 mg, preferably 10.7 mg) (which becomes aCarbonate buffer after the addition of acid); Vial 1 is reconstitutedwith about 3.6-4.4 mL, preferably 4.0 mL of up to 300 mCi ofRadioisotope in 0.1 N HCl; Vial 2 contains a solution of 32.8-40.1 mM,preferably 36.5 mM CaCl₂ where 0.45-0.55 mL, preferably 0.5 mL of thisVial 2 solution is added to the solution of Vial 1; although this vialis often desired, it is optional; this addition must be done prior toadding the second buffer; and Vial 3 contains 0.45-0.55 M, preferably0.5 M Phosphate buffer (pH 7) as a second buffer where 0.45-0.55 mL,preferably 0.5 mL of the solution from this Vial 3 is added to Vial 1.10. The process of claim 8, wherein the drug formulation is a high doseformulation: Vial 1 is a lyophilized mixture prepared from DOTMP (90-110mg, preferably 100 mg), and an empirically determined amount of NaOH(197-241 mg, preferably 219 mg), and NaHCO₃ (97-118 mg, preferably 107mg) (which becomes a Carbonate buffer after the addition of acid); Vial1 is reconstituted with about 36-44 mL, preferably 40 mL of up to 3000mCi Sm-153 (as SmCl₃ solution present with other Sm isotopes such asSm-152) in 0.1 N HCl; Vial 2 contains a solution of 328-401 mM,preferably 365 mM CaCl2 where 4.5-5.5 mL, preferably 5 mL of this Vial 2solution is added to the solution of Vial 1; although this vial is oftendesired, it is optional; this addition must be done prior to adding thesecond buffer; and Vial 3 contains 4.5-5.5 M, preferably 5 M Phosphatebuffer (pH 7) as a second buffer where 4.5-5.5 mL, preferably 5 mL ofthe solution from this Vial 3 is added to Vial
 1. 11. The process ofclaim 8 wherein step a) the Radioisotope is Sm-153 or Lu-177.
 12. Theprocess of claim 8, wherein Vial 2, a Calcium solution, is omitted. 13.The process of claim 8, wherein Vial 2, a Calcium solution, is present.14. A method of treating a mammal having disease causing bone pain, oneor more calcific tumors or needing bone marrow suppression or bonemarrow ablation by administration to said mammal a drug formulation ofclaim
 1. 15. The method of claim 14, wherein the disease is metastaticbone cancer, osteosarcoma or myelodysplastic syndrome.